Table 1.

Influenza Vaccination and Severity of Influenza Disease Analysis for Cases Untreated With Antivirals by Age Category, Before Propensity Score Matching (n = 966)^a

Clinical Outcomes	Influenza Vaccine 2012–13 Season
	50–64 y (n = 328)		65–74 y (n = 232)		≥75 y (n = 406)
	Point Estimate (95% CI)	P Value	Point Estimate (95% CI)	P Value	Point Estimate (95% CI)	P Value
Severe diseaseb (OR)	0.4 (.17; .98)	.04	0.9 (.35; 2.32)	.83	0.76 (.37; 1.54)	.45
Diagnosis of pneumoniac (OR)	0.83 (.47; 1.47)	.53	0.91 (.45; 1.83)	.79	0.85 (.54; 1.33)	.47
Length of hospital stay (RH)d	1.23 (1.02; 1.49)	.03	0.95 (.74; 1.20)	.65	1.20 (1.00; 1.45)	.05

Data excluded: untreated, FluA&B, FluA/B.

Analysis for ICU length of stay was not performed due to small numbers (36, 27, and 37, observations in age groups 50–64, 65–74, and ≥75 years, respectively).

Abbreviations: BMI, body mass index; CI, confidence interval; ICU, intensive care unit; OR, odds ratio; RH, relative hazard.

^aAdjusted for sex, race, BMI, medical condition (asthma, chronic lung disease, cardiovascular disease, chronic metabolic disease, neurologic disease, immunosuppression, renal disease), alcohol abuse, smoking, and influenza virus type.

^bAdmitted to ICU or deceased.

^cAmong those who had a chest X-ray taken within 3 days of admission (n = 932).

^dRH represents hospital discharge accounting for death as a nonindependent competing risk.